Novel filaments and fabrics



Sept. 12, 1961 A. BREEN ET AL 2,999,296

NOVEL FILAMENTS AND FABRICS Filed March 25, 1957 2 SheetsSheet 1 FIG.1 FIG? INVENTORS ALVIN L. BREEN GEORGES PAMM ATTORNEY Sept. 12, 1961 A. 1.. BREEN ETAL NOVEL FILAMENTS AND FABRICS 2 SheetsSheet 2 Filed March 25, 1957 INVENTORS n N R O M n N A E M %M B L S 77 w W W w WE A G a Y B United States 2,999,296 Patented Sept. 12, 1961 2,999,295 NOVEL FILAMENTS AND FABRICS Alvin L. Breen, West Chester, and Georges Pamm', Chadds Ford, Pa., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Mar. 2.5, 1957, Ser. No. 648,421 8 Claims. (CI. 28-78) This invention relates to novel filaments and fabrics and is particularly concerned with the production of fabrics composed of polyester filaments having increased resistance to pilling.

The term pilling signifies the tendency of a fabric composed of staple fibers which may be entirely synthetic or which may be combined with natural fibers such as wool, to develop and collect on its surface small balls of fibers which form as a result of frictional action on the surface of the fiber.

Fabrics composed in whole or in part of polyester staple fibers possess many highly desired characteristics such as high strength, high durability, resistance to deformation and good hand,,drape and feel. However, such fabrics have the disadvantage of being subject to considerable pilling which substantially limits the use of such fabrics in suitings and the like. Considerable effort has been made in the art to find ways and means of overcoming this pilling tendency.

It is an object of this invention to provide novel filaments, fibers and fabrics composed in whole or in part of polyesters. It is a further object of the invention to provide fibers and filaments which, when used in fabrics, exhibit an improved resistance to pilling. A further object is concerned with hollow filaments possessing the property of acquiring a tight and lasting crimp upon relaxation in a suitable shrinking medium such as hot water. Other objects will appear hereinafter.

The objects of the invention can be attained by spinning hollow polyester filaments which may, if desired, have variations in the thickness of the filament wall to induce inherent crimpability. Such hollow filaments have a wide different utility in fabric production, but are especially valuable in the form of staple fibers, particularly when admixed with wool fibers, which are woven or knitted into fabrics having highly improved resistance to pilling.

In the drawings, which illustrate spinning equipment suitable for the production of the filaments of this invention:

FIGURE 1 is a top plan view of the upper plate or filter pack of a spinneret used in the practice of this invention;

FIGURE 1(a) is an elevation view in cross-section of the upper plate or filter pack taken along the lines 1a1a of FIGURE 1. The right-hand half of FIGURE,'1(a) is an elevation in cross-section along the plane of the righthand half of line la-la of FIGURE 1 and the left-hand half of FIGURE 1(a) is an elevation in cross-section along the plane of the left-hand half of line 1a 1a,of FIGURE 1. It will be noted that the two portions of line 1a-1a of FIGURE 1 form an angle at the center of the figure. The two halves of FIGURE 1(a) have been assembled in this fashion in order to show the shape and direction of the different holes and cavities even though they may not fall along the central plane of the spinneret;

FIGURE 2 is a bottom plan view of the apparatus of FIGURE 1 taken at a somewhat difierent angle than FIG-v URE 1, line la-la of FIGURE 2 likewise showing the dual plane cut of FIGURE 1(a);

FIGURE 3 is a top plan view of the bottom plate of aspinneret used in the practice of this invention;

FIGURE 4 is an elevation view in cross-section of the bottom spinneret plate shown in FIGURE 3 with the righthand half shown in the plane of the right-hand half of line 44 of FIGURE 3 (drawn to the center) and with the left-hand half of FIGURE 4 being cut on the plane of the vertical portion (from the center downwardly) of line 44 of FIGURE 3. As in the case of FIGURE 1(a), FIGURE 4 is assembled in the manner indicated to show the shape and direction of the holes and other elements of the bottom spinneret plate although, as is evident from FIGURE 3, these elements are not, in fact, aligned as shown in FIGURE 4;

FIGURE 5 is an elevation view, generally in crosssection, of the upper and lower plates of FIGURES 1, 1(a) 2, 3, and 4, in assembled position utilizing the showing of FIGURE 4 for the lower plate and the showing of co-acting parts of FIGURES 1, 1(a) and 2 for the upper plate or filter pack. FIGURE 5 shows the assembled spinneret with a full showing of the various elements, with the upper plate being shown, as assembled, in the position corresponding to that of the lower plate;

FIGURE 6 is an elevation (magnified and partly in section) of the extrusion pin shown in FIGURE 5;

FIGURE 7 is a cross-section taken on 7--7 of FIG- URE 6;

FIGURE 8 is a cross-section taken on line 8-8 of FIGURE 6;

FIGURE 9 is a cross-section taken on 9-9 of FIG- URE 6;

FIGURE 10 is a view in cross-section showing the details of the lower portion of the pin shown in FIGURE 6 while in operative position in the lower plate of FIG- URES 3 and 4; 9

FIGURE 11 shows a modified form of extrusion pin;

FIGURE 11(a) is a view in cross-section along line 11'(a)11(a) of FIGURE 11;

FIGURE 12 shows an additional form of modified extrusion pin;

FIGURE 12(a) is a view in cross-section along line 12(a)-12(a) of FIGURE 12;

FIGURE 13 is a magnified cross-sectional view of a filament of the invention having a wall of uniform thickness; and

FIGURE 14 is a magnified cross-sectional view of a. filament of the invention of non-uniform wall thickness and having definite crimp characteristics.

It can be seen from the drawings that top plate 1 of the spinneret adapted to receive the filter pack (not shown), has a central chamber ;2 and an annular chamber 3 separated from each other by wall 4. In the bot-tom of chamber 2. are a plurality of holes 5 passing downwardly through plate 1 and diverging outwardly from each other. Holes 5 lead into shallow annular groove 6 formed in the top surface of lower plate 7 which, in assembling the spinneret, is fastened to plate 1 as described below. Holes 8 lead from the bottom of annular chamber 3 vertically downward through plate 1 and terminate at groove 6 of the lower plate 7. Pins 9, provided with longitudinal passages 10 therethrough are positioned in holes 8 with a press fit (and may be further fastened in place by a spline or other means for insuring a tight fit, if desired) with the upper ends of pins 9 extending above the bottom of annular chamber 3 as shown. The press fit of pins 9 may be supplemented by the action of circular serrations 11 provided at the top of pins 9 to grip the inside of holes 8.

Pins 9 are circular in cross-section in the portion 12. in contact with holes 8, as shown in FIGURE 7, having a. diameter sufiicient to give a press fit in holes 8, pins 9 in the major portion 13 passing through plate 7, having a cross-section which is partly areuate (as shown at 13) but which has, as by cutting the pin to form chords in the cross-section of the pins, the general shape of a mutilated triangle as shown in FIGURE 8. Pin 9 then tapers at 14 near its lower part to a smaller, partially arcuate Drawn Tenacity, Dry Elon- Initial Item Denier gmJdenier gation, Modulus Percent Hollow drawn, 160%. 1. 8 3. 8 42 35 Solid drawn, 280%-.- 3.4 3. 6 59 23 It was quite surprising that a lower draw ratio could be used to obtain equivalent tenacity and initial modulus with the hollow filament as compared to a solid filament of the same polymer.

The continuous hollow filaments and control solid filaments described above in this example were cut into staple length and spun into a worsted-count yarn and fabrics woven therefrom. After weaving and finishing under similar conditions, the hollow filament fabric had a greater covering power (15% more cover per unit weight of fiber) than the control fabric. The pilling tendency of the fabric containing hollow filaments was about /3 that of the fabric made from the solid filaments in construction.

Sweaters knitted from the staple made from the hollow filaments made as described above in this example were softer, more luxurious and weighed 40% less than sweaters with the same covering power made from the staple fiber cut from the solid continuous filaments of the polyester.

The spin of this example was repeated, but the gas pressure reduced to. about mm. (gauge) of Water so as to provide a final drawn yarn having 10% gas space by volume. A worsted-type fabric was woven from yarns spun from staple cut from these continuous filaments similar to that above. The fabric from the 10% gascontaining filaments had cover equivalent to that of a solid fiber fabric but weighed 15.5% less. However, the fabric did not exhibit the resistance to pilling possessed by fabrics made from the 50% gas hollow filaments.

A bundle of 50% gas-containing hollow filaments made as above in this example were immersed in a 2% dispersion of the dye Artisil Direct Blue (PR 62) in acetone. After air drying, the filaments were colored medium blue and showed no tendency toward crocking in rubbing off of the dye. When solid filaments of the same polymer were treated in the dye bath, they were stained only a light blue and the dried filaments crooked badl In a similar manner, the hollow filaments of this example, dyed with the vat dye Indigo Violet exhibited freedom from crocking.

Example III A skein of drawn hollow poly(ethylene terephthalate) filaments as prepared in Example I was cut into short lengths with a sharp razor blade. The staple fiber thus prepared was covered with a 5% solution of cellulose acetate in acetone. After one minute, the solution was decanted, the fiber rinsed twice with acetone and the fiber air-dried. Examination of the dried fiber under microscope revealed that the hollow ends of all the fibers were completely sealed by a plug of cellulose acetate, although the individual filaments were not stuck together. The product has an actual density of about 0.7 grain/centimeters (cubic centimeters) with an ap parent density in loosely compacted form of about 0.01 grain/centimeters and floated on water indefinitely with out losing its buoyancy. The product is thus a good substitute for kapok fiber for use in lifebelts and like articles.

A'similar product was obtained by cutting a tow of continuous hollow filaments with'afiying knife staple cutter that had a dull blade. Thepressure of the cut" g effectively sealed the ends of the staple. f I

The thermoplasticity of melt-spun filaments can also be utilized in preparing the permanently-buoyant, low density staple of this example. In order to prevent adhesion between adjacent filaments, a finish containing an aqueous dispersion of a silicone should be applied to the tow of hollow filaments. After drying, the tow is cut by a revolving knife staple cutter that is heated to approximately the fiber melting point and purposely kept somewhat dull. Temperatures below the melting point down to room temperature have been effective also, presumably due to the'heat generated on impact.

A novel product is made by subjecting staple cut fromhollow filament (about 40% voids) of poly(ethylene terephthalate) to a pressure ofabout 10,000 p.s.i.'in a bale crimping cylinder. Partial but random collapse of the hollow spaces occurs so that the fiber bulk is decreased but the fibers display a softer hand in fabric than the uncompressed ones. The use of a stufier box crimper affords a more regular and controlled intermittent collapse of hollow filament structures at sufiiciently high pressures.

Novel effects may be producedby pulsating the flow Example IV A spinneret was madesimilar to Example I except that pin 9 shown with a reduced section 14 through the spinneret plate, is shaped with section 14 being reduced in diameter as compared with portion of pin 9 above the spinneret plate, and with the same'reduced crosssection down to the neck portion 15. Section14of pin 9 is out throughout its length on a chord plane as shown in FIGURES 12 and 12(a) of the drawings thereby providing passage for the molten polymer through thespin neret plate lengthwise of section 14 down to groove'15 in pin 9. Poly(ethylene terephthalate) having a relative viscosity of 36 wasmelt-spun at 280 C. into air at room temperature together with nitrogen (through passage 10 of pin 9) at the gas pressure of Example I with conditions adjusted to give 50% gns-cdntaining' filaments, and the yarn was wound up at 3,000 yards per minute. Without furtherproce ssing the yarn was strong and bulky having much the same properties as the 50% gas space yarns of Example I. It'difiered from the yarn of Example I (which had uniform wall thickness as shown in FIGURE 13. of the drawings) in that the filament wall thickness varied more or less uniformly as shown in FIGURE 14 of thedrawings, with the maximum wall thickness being about twice the wall thickness of the filament section diametrically opposite. This varying wallthickness resulted from the design of pin 9 described above which efiected the feed of more polymer to one side of the spinneret orifice 20 than to the other.

On exposure to boiling water, free of tension, the yarn became tightly coiled with eachfilament taking on a helical configuration, and (as determined by microscopic inspection) with the heavy-walled region of the filament being toward the inner side of the coils. This coiled or crimp'ed yarn showed a high degree of stretchiness when made into knitted fabrics and significant bulkiness in Woven fabrics of suitable construction.

jected "to a pressure in the neighborhood of 10,000

pounds per squareinch with a piston-cylinder type of press. into whicha .mass of yarn is fed, .and random partial collapse I of. the. hollow spaces inthe filaments will occur with interesting application to conversion into textile fabric. having pleasing noveloptical etfcts and fabric hand and feel. sltis preferable, in this application of the invention, .to have agas-polymer .ratio in the fildniehtssuchthat the hollow spaceswill be 40%: or less of-ithe.volume.of-the filament (the polymer constituting 60%90% er. the filament volume) soas toresist too much-collapsepf the filamentsunderthe applied pressure. .L:With .higher1pressures,...e.g.,"40,000 pounds per squaIe..inch,.collapse.-.of the hollow-filaments is almost total with the imparting of acotton-like random ribbonlike form to. the filament whichis also useful to: produce novel eifectswhen processed-into fabric.

While hot water :has been mentioned above as a shrinking. agent for developing crimp, other shrinking agents may be used to effect crimping.

The hollow .extrusionpins in .the spinneret of this in--- ventionrnay .be varied .in .exteriorand interior size as desired For filaments-of regular-cross-section, the hollow .pins are, by virtue .ofthe novel spinneret design, readilytcentered .in .thespinningorifices. However, they may be positioned off-center in the spinning'orifices so as to give filament walls of varying thickness to produce filamentswhich may readily be crimped .on exposure to boiling water, free .oftensiom. as in Example IV.

Althoughthis invention has been illustrated with filamentshaving around crossrsection, it will be obvious to those skilled, in..the art that the spinneret can be modified within the realmof this inventionto spin var ious cross-sections... Thus, by modifying the shape of the orifice (20), cruciform, square, andtriangular cross section shaped filaments may be spun. Such filaments have the advantages of round hollow filaments but confer a different hand to fabrics m'adetherefrom.

The shape of the hollow'core can be modified by changing the shape of passage at the tip of pin 9.

Round fibers having non-round voids such as oval, tri-- angular, squareor-star-shaped may be made. The lat ter two modifications can-:be combined to give non-round:

filaments having non-round voids.

In making hollow filaments as'above described, the gas pressure is preferably slightly above atomspheric pres-' sure so-astoprevent collapse of the filament at the spin-- ning orificesv Thegas pressure at the orifice maybe suitably controlled socas to permit partial shrinkage of the spinning polymer on solidificationbeyond the spinneretor-ifice. In addition to preventing the inherent shrinkage :of: the polymer on solidification of the hollow filaments,.the air pressure may be lessened slightly to permit partial: collapseor. retraction of the tubular filament. This can be done by proper control er the air pressure--in chamber 2 or by suitable design of hole through; pin. 9. It ispreferred that the air pressure in be made lay-placing .apigment in the core, e'.g., byfill ing with-a solution ofiBaCland then treating the fila ment with sulfuric acidpthis product'is opaqueio-X raysi Novel -efiects :are. :obtai'n'e'dby placing lurninescent'mr fluorescent materials Jinthe hollow-core.- r Silver 'or gold mirrors can be deposited on the walls of: the hollow space. Substances such as a halomethylated' 'phosphate' as shown in..U.S. 2,686,769, and like materialscan be placed in the hollowcore to render the filaments flameproof; In all the above mentioned applications, the added substances are protected by the outer layers of the polymer and, hence, are retained in the filament through rough usage.

Any suitable fiber-forming polyester may be used in the practice of this invention. 1 Generallyspeaking,-fiberforming. polyesters will have .a relative viscosity of 22; and above.(.preferab1y 27- 33.), connoting all-{average molecular weight (i.e., number average moleculanweight as obtained by known end group onosmotic pressure-determination). of about 10,000 and upward. Poly (ethyl ene terephthalate) is the preferred polyesten-particular 1y where :heat. stabilization is desired, but other fiber forming polyesters'derived from dicarboxylic acids and from glycols may be. used, e.g., polymers-derived from glycols having two onmore carbon atoms in the chain: and copolymers of ethylene -terephthalate' containing adipic .acid, sebacic-acid,. isophthalicacid, etc. 1 f

The hollow filaments of this invention will normally I be subjected to 'a drawing (permanent stretching) operachamber be not greatly in excess of atmospheric pressure, e.g., not more: than about 30 mm. gage water The hollowproducts described above in the practice of this invention are of great advantage in textile applications; They.confer. greater warmth and covering powerv than solid-filaments at equivalent weights and contype fabric, they have.a significantly lower tendency to pill than fabrics of solid filaments.

Hollow fibers offer aroute to many new and useful products. .-.All manner-of substances,..in-a solution or as,.a;melt, can be.-.=used to fill'the hollow space orcoat the inner wall ofcthetfilamentsby treating thefilamentsin a. vacuums chamhen and thenreleasing the vacuum. A non-abrasive, but delustered -filament, scan tion, .thefilamcnt being preferably drawn from about-two to eight times-its original' undraw-n -length.-1 Prior to drawingythe. filament-s are attenuated, i.e.-, they arev slenderized by pulling the freshly extruded filaments away from the orifices at a little faster than the extrusionrate. %The drawing or, orientation step is;- in addition to attenuation but also has a slenderizing-effect- -The extent of drawingwill depend-on the properties desired in the final filaments, e.g., the drawing will impart ,in-: creased'tenacity to the desired-extent. Furthermore, in the case of crimpable filaments, the drawingwill depend somewhat upon the degree-of eccentric relationship-between the polymer and the hollow core.

This invention is particularly directed to filaments and yarns (i.e., bundlesof filaments, whether continuous-filaments or staple fiber) having denicrs of the magnitude used in textiles. It is preferred that the filaments of this invention have a denier (per filament) in the range of 1 to 10 (inclusive) and that the yarns of this invention havea denier of 30to 8,000 (inclusive).

The hollow filaments of this invention may be advantageously made into woven or knitted textiles without blending with other fibers. Alternatively, they may be blended particularly as staple fibers with other syntheticor artificial fibers or with natural fibers-such as wool,-cotton,- etc., either by blending in the manufacture of the yarn, or by blending yarns composed only-of the filaments and fibers of this invention with yarns of other fibers, during the weaving or knitting operations.

Any variation from the'above description ofthe invention which conforms to sthespirit of the invention is also intended tobe included within the claims.-

We claim:

1. A yarn containing polyester textile staple fibers, said fibers having a continuous void throughout their length, and said polyester having the ester linkages in the polymer chain.

2. The yarn of claim 1 wherein'the staple fibers have a denier of from 1-10.

3. The yarn of claim 1 wherein the polyester of said staple fibers constitutes 60-90% of the volume of the staple fibers.

4. The yarn of claim 1 wherein the continuousvoid in said staple fibers is eccentrically-located. v

5. The yarn of claim 1 having a denier of 30 to 8,000.

9 10 6. A pill-resistant fabric containing polyester textile References Cited in the file of this patent staple fibers, said fibers having a continuous void through- UNITED TAT out their length and said polyester having the ester link- 8 ES PATENTS ages in the polymer Chaim 2, HOlZmann Oct. 17, 1944 7. A pill-resistant fabric comprising yarns having a 5 2399259 Taylm 1946 denier of 30 to 8,000 and which contain polyester textile FOREIGN PATENTS staple fibers, said fibers having a continuous void through- 51 3 Great Britain 14, 1939 out their length, and said polyester having the ester linkages in the polymer chain. OTHER REFERENCES 8. The pill-resistant fabric of claim 7 wherein the con- 10 Dietzsch F German application Serial T8020 tinuous void in said staple fibers is eccentrically located. V11/3e, Printed June 7, 1955 3e 

6. A PILL-RESISTANT FABRIC CONTAINING POLYESTER TEXTILE STAPLE FIBERS, SAID FIBERS HAVING A CONTINUOUS VOID THROUGHOUT THEIR LENGTH AND SAID POLYESTER HAVING THE ESTER LINKAGES IN THE POLYMER CHAIN. 